Plow colter with yieldable force-applying means and adjustable overload mount for colter carrying arm

ABSTRACT

A colter arm having a colter on its rear end is connected to a rockshaft on a mounting bracket and is normally held in a working position by either a spring or a hydraulic cylinder acting between the mounting bracket and a lever arm on the rockshaft so that if the colter encounters an obstruction the spring or hydraulic cylinder will yield to permit the colter to move over the obstruction. The colter arm and one end of the rockshaft have complementary serrated faces which are clamped together to normally hold the colter arm and rockshaft in fixed relative positions. By loosening the bolt clamping the faces together the relative position of the colter arm with respect to the rockshaft can be varied, and, if the colter encounters an extra large obstruction, the bolt will stretch and permit the teeth of the serrated faces to slip and thereby prevent damage to the colter.

United States Patent Hentrich et a1.

[54] PLOW COLTER WITH YIELDABLE FORCE-APPLYING MEANS AND ADJUSTABLEOVERLOAD MOUNT FOR COLTER CARRYING ARM [72] Inventors: Robert DaleHentrich, Bettendorf,

Iowa; Howard Christian Esbeck, Moline; Loren Glenn Arnold, Rock Island,both of I11.

[73] Assignee: Deere & Company, Moline, Ill.

[22] Filed: Jan. 25, 1971 21 Appl. No.2 109,304

[52] US. Cl. ..172/265, 172/270, 172/705 [51] Int. Cl. ..A0lb 61/04 [58]Field ofSearch ..172/139,165,166, 264,

1 1 Oct. 24, 1972 3,545,550 12/1970 Wenzel ..172/572 175,251 3/1876Miller ..172/270 252,279 1/1882 Van Brunt ..172/270 437,651 9/1890 Jones..172/705 Primary Examiner-Robert E. Pulfrey Assistant Examiner-C. W.Hanor Attorney-I-I. Vincent l-larsha, Raymond L. Hollister, Harold M.Knoth, William A. Murray, James M. Nolan and John O. Hayes [57] ABSTRACTlic cylinder will yield to pennit the colter to move over 8 Claims, 5Drawing Figures [5 6] References Cited UNITED STATES PATENTS 3,642,0732/1972 Geurts ..172/180 1,260,076 3/1918 Sherwin ..172/572 3,529,6769/1970 Moe etal ..172/572' 3,405,767 10/1968 Thompson ..172/5721,443,171 1/1923 Dupler ..172/271 3,561,541 2/1971 Woelfel ..172/2653,451,489 6/1969 Sullivan ..172/264 I 26 \l I l 1 4 23\V\40 I13I 6 3o- MPmminwzmz 3.700.037 snmenrz llO INVENTORS R. D. HENTRICH H. C. ESBECK L.G. ARNOLD PLOW COLTER WITH YIELDABLE FORCE- APPLYING MEANS ANDADJUSTABLE OVERLOAD MOUNT FOR COLTER CARRYING ARM BACKGROUND OF THEINVENTION The present invention relates generally to earthworking tools,and specifically relates to a mounting for plow colters.

The use of colters on moldboard plows to cut trash in front of theleading edges of the bottoms has long been known. As safety trip andcushion standards were developed for the bottoms of moldboard plows,there were also proposals for cushion colters or colters that wouldyield upwardly when an obstruction was encountered. One such cushioncolter is illustrated in U. S. Pat. No. 3,451,489 which issued to J. F.Sullivan on 24 June 1969. However, all the previous colter mountingdesigns failed to provide an easy means of adjusting the working depthof the colter and had only" limited clearance when tripped.

SUMMARY OF THE INVENTION The primary objection of the present inventionis to provide a colter mounting which permits the colter to pass overobstructions, such as rocks, without damage to the colter or plow andyet provides a sufficient force on the colter to effectively cut throughtrash.

Another object of the present invention is to provide a cushion mountingfor colters which can use either spring cushion or a hydraulic cushionby changing a few parts.

Still another object of the invention is'to provide a cushion mountingfor a colter which includes an easy means of adjusting the workingposition of the colter.

A further object of the invention is to provide a cushion mounting for acolter which includes a toothed joint in which the teeth will slip toprovide extra clearance when the colter encounters an extra largeobstruction.

The above objects and additional objects and advantages will becomeapparent to those skilled in the art from a reading of the followingdetailed description of two preferred embodiments of the invention whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevation view of a first embodiment of the invention;

FIG. 2 is a top plan view of the first embodiment of the invention;

FIG. 3 is a side elevation view of a second embodiment of the invention;

FIG. 4 is a top plan view of the second embodiment of the invention; and

FIG. 5 is a sectional view taken along the lines 5-5 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,a first embodiment of the invention is illustrated in FIGS. 1 and 2 andincludes a colter l0 rotatably mounted on the rear end of a colter arm12. The forward end of the colter arm is pivotally connected to amounting bracket 14. The mounting bracket 14 includes a pair ofvertically spaced bearing blocks 16 which are rotatably mounted on thelower end of a shank 18. The upper end of the shank is adapted to beclamped to the frame of a plow so that the colter 10 runs in front ofthe leading edge of one of the bottoms. A clamp 20 is secured to theshank 18 between the vertically spaced bearing blocks 16 to verticallyposition the mounting bracket on the shank. The main body of themounting bracket 14 is provided with a recessed area 22 between andrearwardly of the bearing blocks, and a lug 24 on the clamp 20 extendsinto the recessed area so that engagement between the sides of therecessed area and the lug limit rotational movement of the mountingbracket on the shank.

The bracket 14 is provided with a transverse bore in which a rockshaft26 is rotatably mounted. The rockshaft 26 has an enlarged end 28 whichengages the bracket 14 and prevents lateral movement of the rockshaft inone direction. The rockshaft has a through bore and the enlarged end 12thereof is provided with a circular, laterally directed serrated face30. The forward end of the colter arm has a centrally apertured andlaterally directed circular serrated face 32 complementary to theserrated face onthe rockshaft, and a bolt 34 extends through theaperture in the colter arm and through the bore in the rockshaft toclampthe serrated faces together and hold the rockshaft and colter armin fixed relative positions. A washer 36 on the end of the bolt oppositefrom the colter arm has a diameter greater than the diameter of the borein the bracket 14 and engages the bracket to prevent removal of therockshaft 26.

Although the faces 30 and 32 on the'enlarged end of the rockshaft andthe forward end of the colter arm are illustrated and described as beingserrated, those skilled in the art will realize that the same effect canbe achieved by other structure. For example, the faces could be knurled.Therefore, the term serrated as used in the description and claims isintended as a generic description of the equivalent structures.

The enlarged end 28 of the rockshaft 26 has an integral, generallyupwardly extending, lever arm 38 which is forked at its upper end toprovide a pair of spaced anchor ears 40. The cars 40 are apertured toreceive an anchor pin 42 which also extends through an eye 44 on theforward end of a tension link 46. The eye 44 is positioned between thecars 40. A laterally projecting spring abutment 48 on the bracket 14extends to a position to the rear of the lever arm 38 and is providedwith an aperture 50 through which the tension link 46 extends. Thespring abutment is also provided with a rearwardly facing circularrecess 52 which is centered on the aperture 50 and provides a seat forthe forward end of a coil spring 54 which encircles the tension link 46.A spring retainer 56 bears against the rear end of the spring 54 and isretained on the tension link Y 46 by a nut 58.

I means and thus retains the rear end of the colter arm in a lowered,normal working position. However, should the colter 10 encounter anobstruction, the spring 54 will yield and permit the colter to moveupwardly and over the obstruction.

The serrated faces on the rockshaft and the forward end of the colterarm provide a simple adjustment for the colter. By simply loosening thebolt 34, the colter arm can be pivoted about the bolt 34 relative to therockshaft to change the normal working position of the colter withrespect to the bracket without affecting the tension of the spring 54.

The serrated faces on the rockshaft and the forward end of the colterarm also provide a safety feature which prevents damage to the colter.lf the colter encounters an extra large obstruction which requires moreclearance than can be provided by the spring 54, an obstruction whichthe colter cannot pass over when the spring 54 is fully compressed, thebolt 34 will stretch and permit the teeth of the serrated faces 30 and32 to slip so that the colter can move upwardly the distance required toclear the obstruction.

A second embodiment of the invention is illustrated in FIGS. 3-5 of thedrawings and basically differs from the first embodiment of theinvention in that the spring is replaced by a hydraulic cylinderarrangement. The second embodiment includes a colter 110 rotatablymounted on the rear end of a colter arm 112. The forward end of thecolter arm is pivotally connected to a mounting bracket 114. Themounting bracket 114 includes a pair of vertically spaced bearing blocks116 which are rotatably mounted on the lower end of a shank sides Theupper end of the shank is adapted to be clamped to the frame of a plowso that the colter 110 runs in front of the leading edge of one of thebottoms. A clamp 120 is secured to the shank 118 between the verticallyspaced bearing blocks 116 to vertically position the mounting bracket onthe shank. The main body of the mounting bracket 114 is provided with arecessed area 3.12 between and rearwardly of the hearing blocks, and alug 124 on the clamp 120 extends into the recessed area so thatengagement between the side of the recessed area and the lug limitrotational move ment of the mounting bracket on the shank.

The bracket 1 14 is provided with a transverse bore in which a rockshaft126 is rotatably mounted. The rockshaft 126 has an enlarged end 128which engages the bracket 114 and prevents lateral movement of therockshaft in one direction. The rockshaft has a through bore and theenlarged end 128 thereof is provided with a circular, laterally directedserrated face 130. The forward end of the colter arm has a centrallyapertured and laterally directed circular serrated face 132complementary to the serrated face on the rockshaft, and a bolt 134extends through the aperture in the colter arm and through the bore inthe rockshaft to clamp the serrated faces together and hold therockshaft and colter arm in fixed relative positions. A washer 136 onthe end of the bolt opposite from the colter arm has a diameter greaterthan the diameter of the bore in a bracket 114 and engages the bracketto prevent removal 'of the rockshaft 126.

The enlarged end 28 of the rockshaft 126 has an integral, generallyupwardly extending, lever arm 138 which is forked at its upper end toprovide a pair of spaced ears 140. The cars 140 are apertured to receivea pin 142 which mounts a roller 144 between the ears 140. A laterallyprojecting cylinder mount 148 extends to a position to the front of thelever arm 138 and has a large opening which receives a cylinder 146. Thecylinder is slid into the opening from the rear and is provided with aradial lip 150 around its open rear end which engages the cylinder mountto properly position the cylinder. A piston or plunger 152 isreciprocally mounted in the cylinder 146 and its projecting end engagesthe roller 144. A fluid line 154 is connected to the closed forward endof the cylinder 146 and is adapted to be connected to a source of fluidpressure such as an accumulator.

The fluid pressure in the cylinder acts through the plunger 152 to forcethe lever arm 138 rearwardly and the colter downwardly. However, therearward movement of the lever arm is limited by and the normal workingposition of the colter is determined by engagement between lugs 156 and158 on the enlarged end of the rockshaft and the bracket respectively.If the colter encounters an obstruction, the colter arm can move upwardly by forcing fluid out of the cylinder 146.

The serrated faces and 132 on the rockshaft and the forward end of thecolter arm provide the same advantages as in the first embodiment of theinvention. Specifically, they provide for the easy adjustment of theworking position of the colter with respect to the bracket and alsoprovide the increased clearance needed to avoid damage when an extralarge obstruction is encountered.

Due to the unique construction of the colter mounting, many of the partsof the two embodiments are identical and interchangeable. For example,the colter arms and rockshafts for the two embodiments are identical.This has the advantage of lowering manufacturing costs and also make iteasier and cheaper to convert from a spring cushion to a hydrauliccushion or vice versa.

Having described two preferred embodiments of the inventions, variousmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art and these obvious modifications canbe made without departing from the underlying principles of theinvention.

We claim:

1. An adjustable cushion mounting for a colter comprising:

a generally vertical shank; a mounting bracket having vertically spacedjournals mounted on the lower end of the shank for rotary movement; aclamp secured to the shank between the journals to retain the bracket onthe shank; means acting between the clamp and bracket to limit rotarymovement of the bracket on the shank; there being a transverse boreprovided in the mounting bracket; a rockshaft rotatably mounted in thebore and having a projecting end; the projecting end of the rockshaftbeing provided with a serrated face; a generally rearwardly extendingcolter arm having a colter rotatably mounted on the rear end thereof;one side of the forward end of the colter arm being provided with acentrally apertured serrated face complementary to the serrated face onthe rockshaft; bolt means extending through the aperture provided in theforward end of the colter arm and into the rockshaft holding theserrated faces in engagement with the colter arm in an adjusted positionwith respect to the rockshaft and being deformable in a direction normalto the serrated faces when subjected to an extensive tensile force,whereby the position of the colter arm relative to the rockshaft can bevaried byloosening the bolt means; a lever arm provided on theprojecting end of the rockshaft; abutment means provided on the mountingbracket in general alignment with the lever arm; yieldableforce-applying means acting between the lever arm and abutment means toyieldably rotate the rockshaft in a direction to move the colterdownwardly to a normal working position; and stop means acting betweenthe rockshaft and bracket to limit the downward movement of the colterand detennine the nonnal working position of the colter; the parts beingso arranged and constructed that the yieldable forceapplying meansaffords upward movement of the colter when the colter encounters anobstruction, and, if the obstruction requires greater clearance than isafforded by the yieldable force-applying means, the bolt means will bedeformed to permit the teeth of the serrated faces to slip and therebyprevent damage to the colter.

2. The colter mounting set forth in claim 1 wherein the yieldableforce-applying means includes an extensible and retractable hydrauliccylinder means supported by the bracket in engagement with the abutmentmeans and acting against the lever arm on the projecting end of therockshaft.

3. The colter mounting set forth in claim 1 wherein the yieldableforce-applying means includes spring means acting between the abutmentand the lever arm on the projecting end of the rockshaft.

4. The colter mounting set forth in claim 1 wherein the lever arm on theprojecting end of the rockshaft extends generally upwardly, the abutmentmeans includes an apertured lug on the bracket positioned to the rear ofthe lever arm, and the yieldable force-applying means includes a tensionlink having its forward end secured to the lever arm, the tension linkextending through the aperture in the lug and having a threaded rearend, retainer means threaded on the rear end of the tension link, and acoil spring encircling the tension link and having its opposite endsbearing against the lug and retainer means, whereby the coil springnormally yieldably holds the lever arm in a rearward position againstthe lug, and when the colter encounters an obstruction the springpermits forward movement of the lever arm and upward movement of thecolter so that the colter clears the obstruction.

5. The colter mounting structure set forth in claim 1 wherein the leverarm secured to the projecting end of the rockshaft extends generallyupwardly, and the yieldable force-applying means includes a cylindercarried by the bracket in engagement with the abutment means in afore-and-aft position forwardly of the lever arm and having an open endfacing the lever arm, a plunger reciprocally mounted in the cylinder andhaving a projecting end in engagement with the lever arm, and means forconnecting the cylinder to a source of fluid pressure.

6. An adjustable cushion mounting for a colter comprising:

a vertical shank, a bracket having a pair of vertically spaced journalsmounted on the lower end of the shank for rotary movement; a clampsecured to the shank between the journals to retain the bracket on theshank; means acting between the clamp and bracket to limit the rotarymovement of the bracket; there being a transverse bore provided in thebracket; a rockshaft rotatably mounted in the bore and having oneenlarged end which bears against the bracket to prevent lateral movementof the rockshaft in one direction; the enlarged end of the rockshafthaving a serrated face; a central bore extending through the rockshaft;a colter arm having a colter mounted on its rear end and a centrallyapertured and laterally directed serrated face on its forward endcomplementary to the serrated face on the rockshaft; bolt meansextending through the aperture in the colter arm and the bore in therockshaft; a washer having a diameter greater than the bore in thebracket mounted on the end of the bolt means opposite from the colterarm to engage the bracket means, whereby, by tightening the bolt means,the rockshaft is secured in the bore in the bracket and the colter armis retained in an adjusted position relative to the rockshaft; a leverarm on the enlarged end of the rockshaft; abutment means on the bracket;and yieldable force-applying means acting between the lever arm andabutment means to yieldably force the rockshaft and colter arm in onedirection to move the colter to and retain the colter in a normalworking position; whereby, the yieldable force-applying means affordsmovement of the colter when the colter encounters an obstruction, and,if the obstruction requires greater clearance than is afforded by theyieldable force-applying means, the bolt means will stretch to permitthe teeth of the serrated faces to slip and thereby prevent damage tothe colter.

7. An adjustable cushion mounting for a colter comprising: a verticalshank, a bracket having a pair of vertically spaced journals mounted onthe lower end of the shank for rotary movement; a clamp secured to theshank between the journals to retain the bracket on the shank; meansacting between the clamp and bracket to limit the rotary movement of thebracket; there being a transverse bore provided in the bracket; arockshaft rotatably mounted in the bore and having one enlarged endwhich bears against the bracket to prevent lateral movement of therockshaft in one direction; the enlarged end of the rockshaft having aserrated face; a central bore extending through the rockshaft; a colterarm having a colter mounted on its rear end and a centrally aperturedand laterally directed serrated face on its forward end complementary tothe serrated face on the rockshaft; bolt means extending through theaperture in the colter arm and the bore in the rockshaft; a washerhaving a diameter greater than the bore in the bracket mounted on theend of the bolt means opposite from the colter arm to engage the bracketmeans, whereby, by tightening the bolt means, the rockshaft is securedin the bore in the bracket and the colter arm is retained in an adjustedposition relative to the rockshaft; a generally upwardly extending leverarm on the enlarged end of the rockshaft; an apertured lug on the clamppositioned to the rear of the lever arm; a tension link having itsforward end secured to the lever arm; the tension link extending throughthe aperture in the lug and having a threaded rear end; retainer meansthreaded on the rear end of the tension link; and a coil springencircling the tension link and having its opposite ends bearing againstthe lug and retainer means; whereby the coil spring normally yieldablyholds the lever arm in a rearward position against the lug; the coilspring yieldably affords forward movement of the lever arm and upwardmovement of the colter when the colter encounters an obstruction, and,if the obstruction requires greater clearance than is afforded by thecoil springs, the bolt means will stretch to permit the teeth of theserrated faces to slip and thereby prevent damage to the colter.

8. An adjustable cushion mounting for a colter comprising: a verticalshank, a bracket having a pair of vertically spaced journals mounted onthe lower end of the shank for rotary movement; a clamp secured to theshank between the journals to retain the bracket on the shank; meansacting between the clamp and bracket to limit the rotary movement of thebracket; there being a transverse bore provided in the bracket; arockshaft rotatably mounted in the bore and having one enlarged endwhich bears against the bracket to prevent lateral movement of therockshaft in one direction; the enlarged end of the rockshaft having aserrated face; a central bore extending through the rockshaft; a colterarm having a colter mounted on its rear end and a centrally aperturedand laterally directed serrated face on its forward end complementary tothe serrated face on the rockshaft; bolt means extending through theaperture in the colter arm and the bore in the rockshaft; a washerhaving a diameter greater than the bore in the bracket mounted on theend of the bolt means opposite from the colter arm to engage the bracketmeans,

whereby, by tightening the bolt means, the rockshaft is secured in thebore in the bracket and the colter arm is retained in an adjustedposition relative to the rockshaft; means acting between the rockshaftand bracket to limit rotary movement of the rockshaft in a direction tomove the colter downwardly; a generally vertically extending lever armsecured to the enlarged end of the rockshaft; a cylinder secured to thebracket in a fore-and-aft position forwardly of the lever arm and havingan open end facing the lever arm; a plunger reciprocally mounted in thecylinder and having a projecting end in engagement with the lever arm;and means for connecting the cylinder to a source of fluid pressure,whereby, the plunger normally retains the lever arm in a rearwardposition determined by the means acting between the rockshaft andbracket, fluid expelled from the cylinder yieldably affords forwardmovement of the lever arm and upward movement of the colter when thecolter strikes an obstruction, and, if the obstruction requires greaterclearance than is afforded by expelling the fluid from the cylinder, thebolt means will stretch to permit the teeth of the serrated faces toslip and thereby prevent damage to the colter.

1. An adjustable cushion mounting for a colter comprising: a generallyvertical shank; a mounting bracket having vertically spaced journalsmounted on the lower end of the shank for rotary movement; a clampsecured to the shank between the journals to retain the bracket on theshank; means acting between the clamp and bracket to limit rotarymovement of the bracket on the shank; there being a transverse boreprovided in the mounting bracket; a rockshaft rotatably mounted in thebore and having a projecting end; the projecting end of the rockshaftbeing provided with a serrated face; a generally rearwardly extendingcolter arm having a colter rotatably mounted on the rear end thereof;one side of the forward end of the colter arm being provided with acentrally apertured serrated face complementary to the serrated face onthe rockshaft; bolt means extending through the aperture provided in theforward end of the colter arm and into the rockshaft holding theserrated faces in engagement with the colter arm in an adjusted positionwith respect to the rockshaft and being deformable in a direction normalto the serrated faces when subjected to an extensive tensile force,whereby the position of the colter arm relative to the rockshaft can bevaried by loosening the bolt means; a lever arm provided on theprojecting end of the rockshaft; abutment means provided on the mountingbracket in general alignment with the lever arm; yieldableforce-applying means acting between the lever arm and abutment means toyieldably rotate the rockshaft in a direction to move the colterdownwardly to a normal working position; and stop means acting betweenthe rockshaft and bracket to limit the downward movement of the colterand determine the normal working position of the colter; the parts beingso arranged and constructed that the yieldable force-applying meansaffords upward movement of the colter when the colter encounters anobstruction, and, if the obstruction requires greater clearance than isafforded by the yieldable force-applying means, the bolt means will bedeformed to permit the teeth of the serrated faces to slip and therebyprevent damage to the colter.
 2. The colter mounting set forth in claim1 wherein the yieldable force-applying means includes an extensible andretractable hydraulic cylinder means supported by the bracket inengagement with the abutment means and acting against the lever arm onthe projecting end of the rockshaft.
 3. The colter mounting set forth inclaim 1 wherein the yieldable force-applying means includEs spring meansacting between the abutment and the lever arm on the projecting end ofthe rockshaft.
 4. The colter mounting set forth in claim 1 wherein thelever arm on the projecting end of the rockshaft extends generallyupwardly, the abutment means includes an apertured lug on the bracketpositioned to the rear of the lever arm, and the yieldableforce-applying means includes a tension link having its forward endsecured to the lever arm, the tension link extending through theaperture in the lug and having a threaded rear end, retainer meansthreaded on the rear end of the tension link, and a coil springencircling the tension link and having its opposite ends bearing againstthe lug and retainer means, whereby the coil spring normally yieldablyholds the lever arm in a rearward position against the lug, and when thecolter encounters an obstruction the spring permits forward movement ofthe lever arm and upward movement of the colter so that the colterclears the obstruction.
 5. The colter mounting structure set forth inclaim 1 wherein the lever arm secured to the projecting end of therockshaft extends generally upwardly, and the yieldable force-applyingmeans includes a cylinder carried by the bracket in engagement with theabutment means in a fore-and-aft position forwardly of the lever arm andhaving an open end facing the lever arm, a plunger reciprocally mountedin the cylinder and having a projecting end in engagement with the leverarm, and means for connecting the cylinder to a source of fluidpressure.
 6. An adjustable cushion mounting for a colter comprising: avertical shank, a bracket having a pair of vertically spaced journalsmounted on the lower end of the shank for rotary movement; a clampsecured to the shank between the journals to retain the bracket on theshank; means acting between the clamp and bracket to limit the rotarymovement of the bracket; there being a transverse bore provided in thebracket; a rockshaft rotatably mounted in the bore and having oneenlarged end which bears against the bracket to prevent lateral movementof the rockshaft in one direction; the enlarged end of the rockshafthaving a serrated face; a central bore extending through the rockshaft;a colter arm having a colter mounted on its rear end and a centrallyapertured and laterally directed serrated face on its forward endcomplementary to the serrated face on the rockshaft; bolt meansextending through the aperture in the colter arm and the bore in therockshaft; a washer having a diameter greater than the bore in thebracket mounted on the end of the bolt means opposite from the colterarm to engage the bracket means, whereby, by tightening the bolt means,the rockshaft is secured in the bore in the bracket and the colter armis retained in an adjusted position relative to the rockshaft; a leverarm on the enlarged end of the rockshaft; abutment means on the bracket;and yieldable force-applying means acting between the lever arm andabutment means to yieldably force the rockshaft and colter arm in onedirection to move the colter to and retain the colter in a normalworking position; whereby, the yieldable force-applying means affordsmovement of the colter when the colter encounters an obstruction, and,if the obstruction requires greater clearance than is afforded by theyieldable force-applying means, the bolt means will stretch to permitthe teeth of the serrated faces to slip and thereby prevent damage tothe colter.
 7. An adjustable cushion mounting for a colter comprising: avertical shank, a bracket having a pair of vertically spaced journalsmounted on the lower end of the shank for rotary movement; a clampsecured to the shank between the journals to retain the bracket on theshank; means acting between the clamp and bracket to limit the rotarymovement of the bracket; there being a transverse bore provided in thebracket; a rockshaft rotatably mounted in the bore and having oneenlarged end which bears against the bracket to prevent lateRal movementof the rockshaft in one direction; the enlarged end of the rockshafthaving a serrated face; a central bore extending through the rockshaft;a colter arm having a colter mounted on its rear end and a centrallyapertured and laterally directed serrated face on its forward endcomplementary to the serrated face on the rockshaft; bolt meansextending through the aperture in the colter arm and the bore in therockshaft; a washer having a diameter greater than the bore in thebracket mounted on the end of the bolt means opposite from the colterarm to engage the bracket means, whereby, by tightening the bolt means,the rockshaft is secured in the bore in the bracket and the colter armis retained in an adjusted position relative to the rockshaft; agenerally upwardly extending lever arm on the enlarged end of therockshaft; an apertured lug on the clamp positioned to the rear of thelever arm; a tension link having its forward end secured to the leverarm; the tension link extending through the aperture in the lug andhaving a threaded rear end; retainer means threaded on the rear end ofthe tension link; and a coil spring encircling the tension link andhaving its opposite ends bearing against the lug and retainer means;whereby the coil spring normally yieldably holds the lever arm in arearward position against the lug; the coil spring yieldably affordsforward movement of the lever arm and upward movement of the colter whenthe colter encounters an obstruction, and, if the obstruction requiresgreater clearance than is afforded by the coil springs, the bolt meanswill stretch to permit the teeth of the serrated faces to slip andthereby prevent damage to the colter.
 8. An adjustable cushion mountingfor a colter comprising: a vertical shank, a bracket having a pair ofvertically spaced journals mounted on the lower end of the shank forrotary movement; a clamp secured to the shank between the journals toretain the bracket on the shank; means acting between the clamp andbracket to limit the rotary movement of the bracket; there being atransverse bore provided in the bracket; a rockshaft rotatably mountedin the bore and having one enlarged end which bears against the bracketto prevent lateral movement of the rockshaft in one direction; theenlarged end of the rockshaft having a serrated face; a central boreextending through the rockshaft; a colter arm having a colter mounted onits rear end and a centrally apertured and laterally directed serratedface on its forward end complementary to the serrated face on therockshaft; bolt means extending through the aperture in the colter armand the bore in the rockshaft; a washer having a diameter greater thanthe bore in the bracket mounted on the end of the bolt means oppositefrom the colter arm to engage the bracket means, whereby, by tighteningthe bolt means, the rockshaft is secured in the bore in the bracket andthe colter arm is retained in an adjusted position relative to therockshaft; means acting between the rockshaft and bracket to limitrotary movement of the rockshaft in a direction to move the colterdownwardly; a generally vertically extending lever arm secured to theenlarged end of the rockshaft; a cylinder secured to the bracket in afore-and-aft position forwardly of the lever arm and having an open endfacing the lever arm; a plunger reciprocally mounted in the cylinder andhaving a projecting end in engagement with the lever arm; and means forconnecting the cylinder to a source of fluid pressure, whereby, theplunger normally retains the lever arm in a rearward position determinedby the means acting between the rockshaft and bracket, fluid expelledfrom the cylinder yieldably affords forward movement of the lever armand upward movement of the colter when the colter strikes anobstruction, and, if the obstruction requires greater clearance than isafforded by expelling the fluid from the cylinder, the bolt means willstretch to permit the teeth of the serrated faces to slip and therebyprevent dAmage to the colter.